CN116723901A

CN116723901A - Rolling with minimal bending force drop upon entry

Info

Publication number: CN116723901A
Application number: CN202280010471.3A
Authority: CN
Inventors: 安德烈亚斯·霍劳斯; 马蒂亚斯·库尔茨
Original assignee: Primetals Technologies Germany GmbH
Current assignee: Primetals Technologies Germany GmbH
Priority date: 2021-01-18
Filing date: 2022-01-13
Publication date: 2023-09-08
Also published as: US20240075508A1; EP4277756A1; WO2022152781A1; EP4029618A1; JP2024503871A

Abstract

In a rolling stand (1), a planar rolling stock (8) made of metal is rolled. The work roll inserts (5) are pressed apart from each other by a bending system (10). The basic set point (FBB) is provided to a bending feedback controller (14) and the bending feedback controller (14) determines the resultant set point (FB) taking into account the basic set point. The actual value (FB) of the bending force is also provided to the bending feedback controller (14). The bending feedback controller (14) thus determines a basic manipulated variable (SB) of the bending system (10) such that the actual value (FB) is as close as possible to the basic setpoint value (FBB) when the bending system (10) is driven with the basic manipulated variable (SB). From a stabilization point in time (t 3) after the entry point in time (t 2), the bending feedback controller (14) determines a resultant setpoint value (FB) additionally taking into account the actual rolling force (F). During an entry period, which starts before the actual entry time point (t 2) and ends at the latest at the settling time point, an additional set point (FBZ x) is provided to the bending feedback controller (14), which bending feedback controller (14) takes into account when determining the composite set point (FB x). Thereby, the actual value (FB) of the bending force is greater than the basic set value (FBB). Alternatively or additionally, an additional manipulated variable (SZ) is added to the basic manipulated variable (SB), or the adjustment variable (SR) provided to the bending system (10) is limited downward by the minimum manipulated variable (SM).

Description

Rolling with minimal bending force drop upon entry

Technical Field

The invention is based on a method for operating a rolling stand for rolling a flat rolled product made of metal, which has a rolled product head,

wherein the rolling stand has at least a work roll and a backup roll,

wherein the work rolls are mounted in the work roll inserts and a bending system pressing the work roll inserts apart acts on the work roll inserts,

wherein the head of the rolling stock reaches the rolling stand at the actual entry point in time,

wherein the basic set point is provided to a bending feedback controller and the bending feedback controller determines the composite set point taking into account the basic set point,

wherein the bending feedback controller is further provided with an actual value of the bending force,

wherein the bending feedback controller determines the basic manipulated variable of the bending system based on the composite setpoint and the actual value such that the actual value is as close as possible to the composite setpoint when the basic manipulated variable is used to control the bending system,

the bending feedback controller determines the resultant setpoint value starting from a steady point in time after the entry point in time, taking into account additionally the actual rolling forces occurring when rolling flat rolled stock.

The invention is also based on a rolling unit for rolling flat rolling stock made of metal, which rolling unit has a rolling stock head,

wherein the rolling unit has a rolling stand and a bending feedback controller,

wherein the rolling stand has at least a work roll and a backup roll mounted in the work roll insert,

wherein the rolling stand has a bending system for pressing the work roll insert apart,

wherein the bending feedback controller drives the bending system,

wherein the rolling stand and the full controller interact with each other during operation of the rolling unit such that they perform such an operating method.

Background

Rolling stands for rolling flat rolled stock are generally designed as four-roll stands (i.e. rolling stands with work rolls and back-up rolls) or six-roll stands (i.e. rolling stands with work rolls, back-up rolls and intermediate rolls arranged between the work rolls and the back-up rolls). They are typically rolled with metal strips and sometimes also with thick plates.

The rolling table calculation is performed before rolling the corresponding rolled piece. In the context of the rolling table calculation, the setpoint values of the individual actuators of the rolling stand are determined, by means of which the actuators are to be operated when the respective rolled product is rolled. The set point includes at least an adjustment amount or a rolling force. They also generally comprise a set value of the bending force (hereinafter referred to as basic set value) by means of which the work roll insert is pressed and thus also the work roll should be pressed apart. Bending forces may be used to affect the profile, contour and flatness of the product.

Other actuators can also be present to affect the profile, contour and flatness, such as work roll shifting or localized cooling. For stainless steel rolling stands, the strip edges can also be lubricated to affect the profile. However, other actuators are not relevant within the scope of the invention.

The pass mill table calculation is performed by a higher level control device, which is commonly referred to in the industry as an L2 system. The set point determined as part of the pass rolling calculation is forwarded by the control device to a lower level controller, which performs real-time control as the product is rolled. The entire controller is commonly referred to in the professional arts as an L1 system. The set point is specified before the product reaches the gap between the work rolls of the rolling stand (i.e., before entry takes place).

For example, a set point (i.e., a base set point) for the bending force is assigned to the bending feedback controller. The set point is modified during the rolling of the flat product by various correction variables. One of the correction variables is an additional set point which is determined as a function of the rolling force and, like AGC, aims to compensate for the variation of the rolling deformation that occurs due to the variation of the rolling force. However, this additional setting will only be applied after the instability that occurs when the controller of the L1 system again adjusts for entry.

Thus, the bending feedback controller determines the basic manipulated variable for the bending system during an entry period, which starts before the entry time point and ends after the entry time point, based only on the basic set value and the actual value of the bending force, and controls the bending system. This determination is achieved in that the actual value of the bending force is always as close as possible to the basic set point.

Upon entry, the bending force (i.e., its actual value) decreases. The flex feedback controller attempts to correct this drop as soon as possible. However, it takes hundreds of milliseconds (sometimes up to 500 milliseconds) before the system is fully calibrated.

On the one hand, the reduction in bending forces negatively affects the final profile and the associated contour and the flatness of the rolled piece. However, this is generally acceptable. On the other hand, a decrease in bending forces can lead to short-term instabilities, the effect of which on the running of the strip is not always predictable. In particular, it may happen that hooks are formed in the product at the outlet side of the rolling stand. In some cases, the hooks are too large to strike the side rails downstream of the rolling stand. This may lead to damage to the side rails and in some cases even jamming of the head of the product. In this case, the head of the product is not transported any further, but the rolling stand continues to push the product. As a result, the rolled piece is lifted (so-called bulging). This results in at least an unintended long-term interruption of the operation of the rolling stand, sometimes even a serious damage of the rolling stand or of downstream equipment.

DE 102006059 A1 discloses a method for operating a rolling stand for rolling a flat rolled product made of metal, wherein the working rolls of the rolling stand are subjected to bending forces during the period in which the head of the rolled product has not yet arrived. A rolling stand at least as great as the balance forces of the upper work roll and the upper backup roll (and possibly other rolls disposed between the upper work roll and the upper backup roll). From the point where the head of the rolled piece reaches the rolling stand, the bending force is determined according to the process requirements of the rolling process. The bending force generated can be greater or less than the minimum force, and can be greater or less than the equilibrium force.

From JP S57050207 a, a method for operating a rolling stand for rolling a flat rolled product made of metal is known, in which the point in time at which the rolled product head reaches the rolling stand is calculated beforehand. From this point on, the working rolls of the rolling stand are subjected to bending forces by the bending system.

JP S59061512 a discloses a method for operating a rolling stand for rolling a flat rolled product made of metal, wherein a ring lifter arranged upstream of the rolling stand detects whether the rolled product is under tension on the inlet side of the rolling stand. Thereby detecting the entry and exit rolling. Upon entry, the bending forces acting on the working rolls of the rolling stand are adjusted such that the thickness of the rolled product decreases towards its side edges. During the entry process, the bending force is adjusted in a similar manner as soon as a drop in the load on the loop elevator and thus the discharge of the flat product from the upstream roll stand is detected.

DE 4331261 A1 discloses a method for operating a rolling stand for rolling flat rolling stock, in which the working rolls can be subjected to positive and negative bending forces of different magnitudes by means of a bending system.

Disclosure of Invention

The object of the present invention is to provide a possibility to avoid unstable states as much as possible.

This object is achieved by a method of operation having the features of claim 1. Advantageous embodiments are the subject matter of the dependent claims 2 to 7.

According to the invention, an operating method of the type mentioned is designed such that, during an entry period which starts before the actual entry point in time and ends after the actual entry point in time,

-providing additional set points to the bending feedback controller in addition to the basic set points, so that the bending feedback controller determines the resultant set point and the actual value during entry taking into account not only the basic set point but also the additional set point and thus the bending force is greater than the basic set point before the actual entry point in time, and/or

-determining a composite manipulated variable by applying the additional manipulated variable to the base manipulated variable, providing it to the bending system and the bending system is thereby controlled such that the composite manipulated variable is larger than the base manipulated variable, and/or

-feeding the basic manipulated variable and the minimum manipulated variable to the selection element, and the selection element feeding the maximum of the basic manipulated variable and the minimum manipulated variable to the bending system.

If the actual value of the bending force immediately before the entry point in time is greater than the basic set value, the bending force starts to drop at a higher level. This reduces the feasibility and extent of potential hook formation. If the resultant manipulated variable is greater than 0, the hydraulic valve is at least partially opened upon entry, through which hydraulic fluid is supplied to the bending system. Therefore, it is not necessary to open it at the entry point. Thus, the entry of the rolling stock results in less reduction of the bending force. This also reduces the feasibility and extent to which hooks may be formed. By properly specifying additional manipulated variables, it can be ensured that the resulting manipulated variable is greater than 0. For example, the additional manipulated variable can be set to 110% of the maximum possible value. Even if the bending feedback controller determines the minimum possible value as the basic manipulated variable, the hydraulic valve is at least-100% +110% = 10%.

As an alternative to specifying additional manipulated variables, the smallest manipulated variable can also be provided directly. In this case, if the hydraulic valve has been opened by the basic manipulated variable and the minimum manipulated variable is smaller than the basic manipulated variable, the hydraulic valve remains open without changing the open position. Regardless of the value of the basic manipulated variable, however, the hydraulic valve is always open at least to the extent specified by the minimum manipulated variable. By a suitable choice of the minimum manipulated variable (i.e. greater than 0), it can also be ensured in this case that the hydraulic valve is at least partially open at the entry point in time.

The additional set values and/or the additional adjustment amounts and/or the minimum adjustment amounts can be switched suddenly to their maximum values at the beginning of the entry period. The additional setpoint and/or the additional manipulated variable and/or the minimum manipulated variable can also be suddenly reduced to zero at the end of the entry period. Preferably, however, the additional set values and/or the additional manipulated variables and/or the minimum manipulated variables rise strictly monotonically from 0 to their maximum value with a finite gradient from the beginning of the tapping cycle and/or from their maximum value to zero with a finite gradient at the end of the entry period. This results in a smoother transition, which applies less stress to the bending feedback controller, the hydraulic valve and the bending system, among other things, and also results in a more stable transition, especially when additional set points and/or additional manipulated variables and/or additional set points and/or additional manipulated variables. The minimum manipulated variable is reduced to 0.

The feasibility of raising and lowering with limited slopes is well known and familiar to those skilled in the art. For example, a ramp can occur or the binary switching process can be smoothed by appropriate filtering.

Typically, the expected point in time of entry is determined by path tracking of the product. In this case, the start point of the entry period is preferably earlier than the desired entry point in time by a predetermined advance period.

The predetermined advance period is determined, for example, in such a way that: the additional setpoint value and/or the additional manipulated variable and/or the minimum manipulated variable reaches its maximum value at a point in time which is at least as great as the error tolerance between the actual and the expected entry point in time. The person skilled in the art is able to easily estimate the wrong tolerances based on the inaccuracy of the path of the head of the rolled piece, as it is known. The predetermined period of time is typically in the range between 0.5s and 2.0s, in particular between 0.8s and 1.5s, for example about 1.0s.

The end of the entry period can be a predetermined amount of delay time after the expected entry point in time. Preferably, however, the end of the entry period is a predetermined lag period after the actual entry point in time. For example, the actual entry point in time can be easily detected due to a sudden increase in the actual rolling force or the rolling torque actually applied by the driving means of the work rolls.

In both cases, the predetermined later period is determined such that the point in time at which the additional set point and/or the additional manipulated variable and/or the minimum manipulated variable maintain their maximum values until the distance from the intended or actual tapping point has a predetermined value. From this point in time, the additional setpoint and/or the additional manipulated variable and/or the minimum manipulated variable can be reduced to 0. The specified value, i.e., the additional set point and/or the period of time during which the additional manipulated variable and/or the minimum manipulated variable remain at their maximum values, is determined by the design and size of the bending system. This value is generally in the range between 0.1s and 1.0s, in particular between 0.2s and 0.6s, for example 0.3s or 0.4s.

Preferably, the additional set point values and/or the additional manipulated variables and/or the maximum values of the minimum manipulated variables are determined before rolling the flat rolled product as a function of the properties of the rolled product and/or as a function of the desired rolling force. The corresponding maximum value can thus be optimally matched to the particular rolling pass to be performed. Alternatively or additionally, the additional setpoint values and/or the maximum values of the additional manipulated variables and/or the minimum manipulated variables can be determined in such a way that the composite manipulated variable assumes its maximum possible value immediately before the actual entry point in time. This measure is particularly useful in the case of the front stands of a multi-stand finishing train or in the case of the rolling stands (plate rolling mill) used for rolling thick plates.

The additional set value and/or the additional manipulated variable and/or the minimum manipulated variable are preferably determined such that a drop in the actual value of the bending force is compensated for by at least 50% at the actual entry point in time, which is to be set without the additional set value and/or the additional manipulated variable and/or the minimum manipulated variable. Thus, if the basic setpoint value has a value X and no additional setpoint value and/or additional manipulated variable and/or minimum manipulated variable achieve a drop to a value Y upon entry, the additional setpoint value and/or additional manipulated variable and/or minimum manipulated variable are preferably determined such that the bending force drops to a maximum value (x+y)/2, preferably even only to a value greater than (x+y)/2. It is particularly preferred that the bending force drops to a maximum value of the basic set point, i.e. the value X.

This object is further achieved by a rolling unit having the features of claim 8. According to the invention, in a rolling unit of the type mentioned at the beginning, the rolling stand and the bending feedback controller interact with each other during operation of the rolling unit such that they perform the operating method according to the invention.

Drawings

The above-mentioned features, features and advantages of this invention, and the manner of attaining them, will become more apparent and be better understood by reference to the following description of embodiments taken in conjunction with the accompanying drawings. This is shown in the schematic:

figure 1 shows the rolling stand from the side before rolling the rolled product,

fig. 2 shows the rolled product in fig. 1 from the side, i.e. at the start of rolling of the rolled product,

figure 3 shows the rolling stand of figure 1 from the side during rolling of a rolled piece,

figure 4 shows from the front a part of the rolling stand of figures 1 to 3,

figure 5 shows a part of the control structure of the rolling stand of figures 1 to 4,

figure 6 shows a timing diagram of the method of operation of the rolling stand of figures 1 to 4 according to the prior art,

figure 7 shows a part of the control structure of the rolling stand of figures 1 to 4 according to a first embodiment of the invention,

figure 8 shows a timing diagram of the method of operation of the rolling stand of figures 1 to 4 according to a first embodiment of the invention,

figure 9 shows a part of the control structure of the rolling stand of figures 1 to 4 according to a second embodiment of the invention,

fig. 10 shows a timing diagram of a method of operating the rolling stand of fig. 1 to 4 according to a second embodiment of the invention;

fig. 11 shows a part of a control structure for the rolling stand of fig. 1 to 4 according to a third embodiment of the invention.

Detailed Description

According to fig. 1 to 4, a rolling stand 1 has work rolls 2 and backup rolls 3. Within the scope of the invention, this represents a minimum configuration of the rolling stand 1. Furthermore, the rolling stand 1 can also have intermediate rolls. In this case, the intermediate roll will be arranged between the work roll 2 and the backup roll 3. As shown in fig. 4, the work roll 2 has a bearing journal 4 through which the work roll 2 is mounted in the work roll insert 5. In a similar manner, the support roll 3 has a bearing journal 6 by means of which the support roll 3 is mounted in a support roll insert 7.

When rolling the rolled piece 8, the rolling force F is applied to the backup roll insert 7 and thus also to the backup roll 3. The rolling force F is transmitted to the work rolls 2 via the backup rolls 3. As is well known to those skilled in the art. The rolling stock 8 itself is made of metal, for example steel or aluminum. It is a flat rolled piece, such as a strip or slab. The rolling stock 8 has a rolling stock head 9. The product head 9 is the region of the product 8 that is first rolled in the rolling stand 1. Accordingly, the transport direction of the rolling stock 8 is denoted by x in fig. 1 to 3.

The rolling stand 1 also has a bending system 10. The bending system 10 generally comprises at least two hydraulic cylinder units 11, 12 which act on the drive side and the operator side of the work roll insert 5 in order to press the work roll insert 5 apart. The bending system 10 is used to adjust the profile, contour and flatness of the product 8. In some cases, a plurality of hydraulic cylinder units 11, 12 acts on the work roll insertion portion 5, respectively. In this case, there are correspondingly more hydraulic cylinder units 11, 12.

According to fig. 5, the rolling stand 1 is controlled by a control structure. The control structure generally comprises a control device 13 and in any case a bending feedback controller 14.

The control device 13 is an upper control device functioning as an L2 system, i.e. it determines their set values in the context of the calculation of the rolling table of the lower feedback controller. In fig. 5, only a single feedback controller, namely the bending feedback controller 14, is shown. Of course, in practical applications, other feedback controllers are also possible. However, only the bending feedback controller 14 is important within the scope of the present invention. Accordingly, only the bending feedback controller 14 is shown and only the bending feedback controller 14 is described below.

The rolling table calculation is performed on the rolled product 8 even before the rolled product 8 is rolled in the rolling stand 1 (see fig. 1). In the context of the calculation of the rolling table, the control device 13 determines the set point for the adjustment of the rolling stand 1, which can be a roll offset or the like. In particular, in the context of a rolling gauge calculation for rolling a product 8 in a rolling stand 1, the control device 13 determines a basic set point FBB of the bending force. The basic set value FBB can be a single odd value that is constant over time. Alternatively, separate basic setpoint values FBB can be determined for different portions of the strip to be rolled. In this case, the basic setting FBB varies with time.

The basic setting FBB is supplied to the bending feedback controller 14 from the time point t1 (see fig. 6). The time point t1 is hereinafter referred to as a default time point t1. At a default time t1, the product head 9 has not yet reached the rolling stand 1 (see fig. 1). The basic set value FBB is normally provided by the control means 13. In principle, however, the basic set value FBB can also be provided to the bending feedback controller 14 in some other way.

The actual value FB of the bending force is also provided to the bending feedback controller 14. The feasibility of detecting or determining the actual value FB is generally known to a person skilled in the art. For example, the working pressures pP, pT in the working spaces of the hydraulic cylinder units 11, 12 can be mathematically linked to each other in combination with the effective working area in order to determine the bending force FB.

The bending feedback controller 14 controls the bending system 10. In particular, the bend feedback controller 14 uses the resulting setpoint FB and the actual value FB to determine the base manipulated variable SB of the bending system 10. The basic manipulated variable SB is determined such that if the bending system 10 is controlled by the basic manipulated variable SB, the actual value FB is as close as possible to the synthetic set value FB. The resultant set point FB is determined by the bending feedback controller 14 using at least the basic set point FBB. The synthesized setpoint FB can be temporarily the same as the basic setpoint FBB. However, at least temporarily, other variables are also included in the composition set point FB. As will become apparent. The bending feedback controller 14 uses the base manipulated variable SB to determine the resultant manipulated variable SR. The composite manipulated variable SR can be temporarily identical to the basic manipulated variable SB. In normal operation, i.e. during steady rolling of the flat rolled piece 8, the bending feedback controller 14 outputs the resultant manipulated variable SR to the bending system 10, thereby controlling the bending system 10.

The working space of the hydraulic cylinder units 11, 12 is subjected to a high working pressure pP (pump pressure) and a low working pressure pT (tank pressure) by the bending feedback controller 14 determining in particular the opening state of the hydraulic valves 15, 16 as basic manipulated variable SB and as synthetic manipulated variable SR. The hydraulic valves 15, 16 are typically continuously adjustable valves, i.e. proportional or servo valves.

Due to the provision of the basic setpoint FBB, the bending feedback controller 14 therefore first determines from the default time t1 a relatively large basic manipulated variable SB, even the maximum possible value MAX of the basic manipulated variable SB (and of the synthetic manipulated variable SR). However, once the actual value FB of the bending force is as close as possible to the basic set value FBB, it reduces the basic manipulated variable SB back to 0 or almost zero. In this connection, it should be pointed out that, within the scope of the invention, a positive value of the basic manipulated variable SB corresponds to an increase in bending force (reaching the technically maximum possible value) and a negative value corresponds to a decrease in bending force.

At time t2, the product head 9 reaches the rolling stand 1 (see fig. 2). The time point t2 is hereinafter referred to as the actual entry time point t2. The actual entering period t2 can be easily detected, for example, by recognizing a significant increase in the rolling force F or rolling torque of the driving of the work rolls 2. Upon entry, the bending force FB drops significantly. A 50% or even more drop is highly likely. In a relatively short time, the bending feedback controller 14 opens the hydraulic valves 15, 16 by specifying the respective basic manipulated variable SB, thereby setting the bending force back to its resultant set point FB. The time required to recover the bending force is typically well below 1s, for example about 500ms.

After the actual entry time t2, the rolling of the rolling stock 8 is effected (see fig. 3). However, immediately after the entry point t2, the rolling stand 1 is in a relatively unstable state, which is again corrected by the various feedback controllers (including the bending feedback controller 14) assigned to the rolling stand 1. The steady state is reached again at the steady time point t 3. The time interval between the stabilization point in time t3 and the entry point in time t2 is determined by the design and the dimensions of the rolling stand. Typically, the time interval is in the range of 1s or less, for example 500ms or less.

From the stabilization time point t3, a correction value δfb is determined by the evaluation unit 17. The correction value δfb is applied to the basic setting value FBB. From the stabilization time point t3, the synthesis set value FB is the sum of the basic set value FBB and the correction value δfb. The correction value δfb is determined in the evaluation unit 17 from the (actual) rolling force F. The evaluation unit 17 thus implements the so-called DPC (= "bent AGC").

If desired, additional correction variables can also be provided to the bending feedback controller 14 from the stabilization point in time t3, for example from flatness feedback control or from profile feedback control. Correction based on thermal influencing factors is also possible. However, at least compensation of the effect caused by the rolling force is given.

At time t4, the roll leg 18 (see fig. 1 to 3) of the roll 8 is removed from the machine frame 1. Similarly to the actual entry time t2, the actual exit time t4 can also be easily detected, in particular by detecting a significant drop in the rolling force F or the rolling torque of the drive of the work rolls 2. The time point t4 is hereinafter referred to as the departure time point. In general, the application of the correction value δfb to the basic setting value FBB is frozen shortly before the departure time t4, i.e. the last determined correction value δfb is retained. However, this is minor within the scope of the invention.

The core of the prior art process described above is preserved but modified and supplemented in accordance with the present invention. Possible modifications and additions are explained in more detail below in connection with fig. 7 and 8, in more detail in connection with fig. 9 and 10, and in more detail in connection with fig. 11.

As part of the embodiment according to fig. 7 and 8, in addition to the basic set point FBB, an additional set point FBZ is provided to the bending feedback controller 14 during the entry period. The additional set value FBZ can be fed by the control means 13 to the bending feedback controller 14. However, the additional setting can also be specified in some other way, for example by an operator (not shown).

The entry period starts at a start time point t5 and ends at an end time point t6. The start time point t5 is earlier than the actual entry time point t2. The end time point t6 is later than the actual entry time point t2. The end time point is typically before the stabilization time point t 3. The end time point can also coincide with the stabilization time point t 3. However, the end time t6 should at least generally not be after the stabilization time t 3. Since the meaning and purpose of the feedback control of the rolling stand 1 is no longer to guarantee a stable start of the rolling process, starting from the stabilization point in time t 3. Instead, the meaning and purpose of the feedback control of the rolling stand 1 is now to roll the product 8 to its target properties, in particular its target thickness and its target profile or its target contour. The provision of the additional setpoint FBZ beyond the steady-state point in time t3 is disadvantageous for this.

The additional set point FBZ is applied to the basic set point FBB. The additional set value FBZ is provided to the bending feedback controller 14 such that the bending feedback controller 14 determines the sum of the basic set value FBB and the additional set value FBZ as the resultant set value FB. The basic manipulated variable SB is thus determined in such a way that the actual value FB of the bending force is as close as possible to the sum. Since the modified set value (fbb+fbz instead of FBB), the actual value FB of the bending force immediately before the entry time point t2 is larger than the basic set value FBB.

In the context of the embodiment according to fig. 9 and 10, the additional manipulated variable SZ is applied to the basic manipulated variable SB during the entry period. The sum of the basic manipulated variable SB and the additional manipulated variable SZ is thereby supplied as a resultant manipulated variable SR to the hydraulic valves 15, 16. Thus, the synthesized manipulated variable SR is larger than the basic manipulated variable SB immediately before the actual entry time point t2. The additional manipulated variable SZ can be provided by the control device 13 to the bending feedback controller 14. However, it can also be specified in some other way, for example by an operator (not shown).

In the embodiment according to fig. 9, the basic actuating variable SB and the additional actuating variable SZ are added at the output side of the bending feedback controller 14. On the other hand, in the embodiment according to fig. 11, the basic manipulated variable SB and the minimum manipulated variable SM are provided to the selection element 19 on the output side of the bending feedback controller 14. The selection element 19 selects the larger of the manipulated variables SB, SM provided thereto and provides the selected manipulated variable to the bending system 10 as the resultant manipulated variable SR. In this embodiment, on the one hand, no additional setpoint FBZ has to be specified, since the bending feedback controller 14 can make the combined manipulated variable SR larger than the minimum manipulated variable SM. However, the bending feedback controller 14 cannot make the resultant manipulated variable SR smaller than the minimum manipulated variable SM. Thus, the minimum manipulated variable defines a minimum actuation state of the bending system 10.

In general, it is sufficient to employ the procedure according to fig. 7 and 8 or the procedure according to fig. 9 and 10. In principle, however, it is also possible to combine these two processes with one another. For example, the additional manipulated variable SZ can be mainly applied such that the actual value FB of the bending force increases. In this case, the additional set value FBZ can be updated accordingly at the same time so that the bending feedback controller 14 does not counteract the increase in bending force due to the deviation of the actual value FB of the bending force from the basic value set value FBB. However, even if the additional set value FBZ is not updated, the resultant manipulated variable SR can be made necessarily positive. All that is required for this is to select a sufficiently large additional manipulated variable SZ. The design according to fig. 11 generally does not have to be combined with one of the designs of fig. 7 to 10.

The various advantageous embodiments of the invention can also be seen in particular from fig. 8 and 10, and in individual cases from fig. 7 and 9. As a result, the same applies to the design of fig. 11. These designs are not necessary to implement the basic principles of the present invention, but they provide additional advantages. These designs will be individually explained in more detail below. They can be implemented independently of one another, but can also be combined with one another as desired. Furthermore, the design is explained below without exception in connection with fig. 8 and part of fig. 7, i.e. for the case where the additional set value FBZ is specified. However, if the additional manipulated variable SZ or the minimum manipulated variable SM is specified, an advantageous design can also be realized in a completely similar manner.

A possible design involves a way to specify the additional set value FBZ from the start time point t 5. In particular, the additional set value FBZ preferably rises strictly monotonically from the starting point in time t5 and with a finite slope from 0 to the maximum value FBZ 0. This increase can occur for a period of time in particular in the range of a few hundred milliseconds. The lifting should be completed before the actual entry point in time t2. Suitable steps for gradual rise are well known to those skilled in the art.

Another possible embodiment relates to the way of lowering the additional set value FBZ after the actual entry time t2. In particular, the additional set point FBZ decreases from its maximum FBZ0 to 0, preferably in a strictly monotonic manner and with a limited slope. In particular, the period of time in which such a reduction occurs can also be in the range of hundreds of milliseconds. The corresponding step of gradual decrease is well known to those skilled in the art. However, at the latest, the value 0 must be reached at the stabilization time point t 3.

Another possible embodiment involves the definition of the starting point in time t 5. In particular, the expected entry point in time t7 can be determined as part of the path tracking of the product head 9 (the implementation of the path tracking is generally known to those skilled in the art). Therefore, the start time point T5 can be easily determined so as to be earlier than the expected entry time point T7 by the predetermined period T1.

The actual entry time point t2 can be before or after the expected entry time point t7. However, the time deviation is at most as large as the previously known error tolerance δt. Thus, the actual entry time t2 is in the interval [ t7- δt; t7+ deltat ].

The predetermined advance period T1 can in particular be measured such that the additional setpoint value FBZ has already reached its maximum value FBZ0 explicitly at the actual entry time T2. In particular, this embodiment makes it possible to ensure that the actual value FB of the bending force has been set as far as possible to the sum of the basic setpoint value FBB and the additional setpoint value FBZ. Alternatively, the predetermined advance period t1 can also be measured in such a way that the additional set value FBZ must not have reached its maximum value FBZ0 at the actual entry point in time t2. This embodiment can ensure in particular that the resultant manipulated variable SR has a positive value at the actual entry point in time t2. The predetermined period T1 is generally in the range between 0.5s and 2.0s, in particular between 0.8s and 1.5s, for example about 1.0s.

The specific way of determining the advance period T1 can also be combined with the specific way of determining the additional set value FBZ (or its maximum value FBZ 0). In particular, the advance period T1 can be determined in such a way that at the actual entry point in time T2 the "bending force FB has been adjusted as much as possible to the sum of the basic set value FBB and the additional set value FBZ. At the same time, the additional set point FBZ (or its maximum FBZ 0) can be determined such that the actual value FB of the bending force does not reach the sum of the basic set point FBB and the additional set point FBZ at all. (hence, the above expression has been placed in quotation marks). As a result of this step, the resultant manipulated variable SR is forced to become positive (typically even up to the maximum MAX) and to remain at that value, since the actually desired result (fb=fbb+fbz) cannot be achieved.

Another possible embodiment involves the definition of the end time t6, while satisfying the condition that the end time t6 is no later than the stabilization time t 3. Because, as already mentioned, the actual entry point in time t2 can be recorded without difficulty or can be determined on the basis of the recorded measurement variables. Therefore, the end time point T6 can be determined without problems such that it is later than the actual entry time point T2 by a predetermined lag time period T2.

The predetermined lag time period T2 is preferably dimensioned in such a way that the additional set value FBZ maintains its maximum value FBZ0 until a point in time at which the distance from the actual entry point in time T2 has a predetermined value. In particular, this value can range between 0.1s and 1.0s. For example, it can be between 0.2s and 0.6 s. Values between 0.3s and 0.4s are particularly preferred. After the latter point in time, the additional set point FBZ may suddenly, preferably gradually, decrease from its maximum value FBZ0 to 0. Reaching a value of 0 corresponds to the end time point t6. Since the period of time during which the additional set value FBZ decreases is also known, the end time t6 can be determined without difficulty based on the actual entry time t2.

Alternatively, the predetermined lag period T2 can be determined based on the expected entry point in time T7. In this case, the determination is not based on the actual entry time point t2, but is based on the expected entry time point t7.

Another possible embodiment relates to the determination of the additional set value FBZ (or its maximum value FBZ 0), for example by the control device 13. In particular, the characteristics of the rolled stock 8 can be utilized. These properties are, on the one hand, the actual or expected variables of the rolled product 8 that the rolled product 8 has before rolling in the rolling stand 1 or is supposed to have. Examples of these variables are width, thickness, temperature and chemical composition, and can also be a pretreatment of the rolled stock 8. On the other hand, these properties are the target variables that the product 8 should have after rolling in the rolling stand 1. Examples of these variables are the width and thickness of the rolled piece 8. Furthermore, the mechanical properties of the rolling stand 1 are known, such as the modulus of elasticity of the stand, the diameter of the work rolls 2, the diameter of the support rolls 3, etc. Finally, a desired value of the operating variable of the rolling stand 1 for rolling the rolled stock 8, in particular a desired value FE of the rolling force F, is determined, for example by the control device 13, as part of the rolling table calculation. The additional setpoint FBZ or its maximum FBZ0 is preferably determined as a function of the properties of the rolled product 8 and/or the desired value FE of the rolling force F. If necessary, additional consideration can be given to the mechanical properties of the rolling stand 1. The specific determination can be performed using a formula or a table, for example. The formula or table can be stored, for example, in the control device 13.

Another possible embodiment also relates to the manner in which the additional setpoint FBZ or its maximum FBZ0 is determined. In particular, the additional setpoint FBZ can be determined such that the resultant manipulated variable SR assumes its maximum possible value immediately before the actual entry point in time t2. The determination of the additional set value FBZ results in the hydraulic valves 15, 16 being fully opened at the actual entry point in time t2 and thus the entire operating pressure pP of the hydraulic system (including the accumulator) being steadily entered. This step can be applied in particular to the front rolling stands (in the case of metal strips) of thick plate stands and multi-stand finishing stands. In principle, however, this step can also be applied to the post-rolling stands of a multi-stand finishing mill group.

A last possible embodiment also relates to the way in which the additional set value FBZ or its maximum value FBZ0 is determined. In particular, the additional set value FBZ can be determined in such a way that the actual value FB of the bending force drops at the actual entry point in time t2, which would be compensated for by at least 50% if the additional set value FBZ was not provided to the bending feedback controller 14.

In many cases it is sufficient if the hydraulic valves 15, 16 are not fully open but only slightly open. In particular, a design is useful in which the minimum manipulated variable SM is specified and has a relatively low value, for example a value between 8% and 20% of the maximum possible modulation of the hydraulic valves 15, 16. However, it should not be excluded that in other cases a larger minimum manipulated variable SM is specified.

The present invention has a number of advantages. In particular, the access is significantly stabilized. Furthermore, the period of time that elapses from the entry time point t2 to the actual value FB of the bending force reaching the basic set value FBB again shortens. Finally, the thread processing and the rolling processing are also stable.

While the invention has been particularly shown and described with reference to a preferred embodiment, the invention is not limited to the disclosed example and other variants can be derived therefrom by those skilled in the art without departing from the scope of the invention.

List of reference numerals

1. Rolling stand

2. Work roll

3. Support roller

4. 6 bearing journal

5. Work roll insertion portion

7. Backup roll insert

8. Rolled piece

9. Head of rolled piece

10. Bending system

11. 12 hydraulic cylinder unit

13. Control device

14. Bending feedback controller

15. 16 hydraulic valve

17. Evaluation unit

18. Rolled piece foot

19. Selection element

F rolling force

FE expected value

FB synthesis set point

FBB basic set value

FBZ additional set point

Maximum value of FBZ0

Actual value of FB bending force

MAX maximum feasible value

pP, pT working pressure

SB basic manipulated variable

SM minimum manipulated variable

SR synthetic manipulated variable

sZ additional manipulated variable

time points t1 to t7

Time period T1, T2

X direction of transmission

δFB correction value

δt error tolerance.

Claims

1. A method for operating a rolling stand (1) for rolling a flat rolled product (8) made of metal, said rolled product having a rolled product head (9),

wherein the rolling stand (1) has at least a work roll (2) and a backup roll (3),

wherein the work roll (2) is mounted in a work roll insert (5) and a bending system (10) pressing the work roll insert (5) apart acts on the work roll insert (5),

wherein the rolling stock head (9) reaches the rolling stand (1) at the actual entry point (t 2),

wherein a basic set point (FBB) is provided to a bending feedback controller (14) and the bending feedback controller (14) determines a composite set point (FB) taking into account the basic set point (FBB),

wherein the bending feedback controller (14) is further provided with an actual value (FB) of the bending force,

-wherein the bending feedback controller (14) determines a basic manipulated variable (SB) of the bending system (10) from the composite setpoint (FB) and the actual value (FB) such that the actual value (FB) is as close as possible to the composite setpoint (FB) when controlling the bending system (10) with the basic manipulated variable (SB),

-wherein the bending feedback controller (14) determines the resultant setpoint value (FB) taking into account an actual rolling force (F) occurring during rolling of the flattened rolled piece (8) starting from a stabilization point in time (t 3) after an entry point in time (t 2),

it is characterized in that the method comprises the steps of,

during an entry period starting before the actual entry point in time (t 2) and ending after the actual entry point in time (t 2),

-providing an additional set point (FBZ) to the bending feedback controller (14) in addition to the basic set point (FBB), such that the bending feedback controller (14) determines the resultant set point (FB) during the entry period taking into account not only the basic set point (FBB), but also the additional set point (FBZ), and whereby the actual value (FB) of the bending force is greater than the basic set point (FBB) immediately before the actual entry point (t 2), and/or

-determining a composite manipulated variable (SR) by applying an additional manipulated variable (SZ) to the basic manipulated variable (SB), the composite manipulated variable being provided to the bending system (10), and the bending system (10) being thus controlled such that the composite manipulated variable (SR) is larger than the basic manipulated variable (SB) and/or

-providing the basic manipulated variable (SB) and the minimum manipulated variable (SM) to a selection element (19), and the selection element (19) providing the maximum of the basic manipulated variable (SB) and the minimum manipulated variable (SM) to the bending system (10).

2. The operating method according to claim 1, characterized in that the additional setpoint value (FBZ x) and/or the additional manipulated variable (SZ) and/or the minimum manipulated variable (SM) increases from 0 to a maximum value (FBZ 0 x) with a limited slope and/or decreases from a maximum value (FBZ 0 x) to zero with a limited slope at the end (t 6) of the entry period starting from the start (t 5) of the entry period.

3. Method of operation according to claim 1 or 2, characterized in that an expected entry time point (T7) is determined by means of the path tracking of the rolling stock (8), and the start point (T5) of the entry time period is earlier than the expected entry time point (T7) by a predetermined advance time period (T1).

4. A method of operation according to claim 1, 2 or 3, characterized in that the end point (T6) of the entry period is later than the actual entry point (T2) by a predetermined lag period (T2).

5. Method according to any of the preceding claims, characterized in that the maximum value of the additional set value (FBZ x) and/or of the additional manipulated variable (SZ) and/or of the minimum manipulated variable (SM) is determined as a function of the properties of the rolled product (8) and/or as a function of the intended rolling Force (FE) before rolling the rolled product (8) in the rolling stand (1).

6. The operating method according to any one of the preceding claims, characterized in that the maximum value of the additional setpoint value (FBZ), and/or of the additional manipulated variable (SZ), and/or of the minimum manipulated variable (SM) is determined such that the synthetic manipulated variable (SR) assumes a maximum possible value (MAX) of the synthetic manipulated variable at the actual entry point in time (t 2).

7. The operating method according to any one of the preceding claims, characterized in that the additional setpoint value (FBZ) and/or the additional manipulated variable (SZ) and/or the minimum manipulated variable (SM) are determined such that a drop in the actual value (FB) of the bending force is compensated for by at least 50% at the actual entry point in time (t 2), wherein the actual entry point in time is adjusted without the additional setpoint value (FBZ) and/or the additional manipulated variable (SZ) and/or the minimum manipulated variable (SM).

8. A rolling unit for rolling a flat rolled stock (8) made of metal, said rolled stock having a rolled stock head (9),

wherein the rolling unit has a rolling stand (1) and a bending feedback controller (14),

wherein the rolling stand (1) has at least a work roll (2) and a backup roll (3) mounted in a work roll insert (5),

wherein the rolling stand (1) has a bending system (10) for pressing the work roll insert (5) apart,

-wherein the bending feedback controller (14) actuates the bending system (10), characterized in that,

the rolling stand (1) and the bending feedback controller (14) interact with each other during operation of the rolling unit such that the rolling stand and the bending feedback controller perform the method of operation according to any of the preceding claims.